This invention relates to the production of cyclopentadiene metal compounds, such as those of iron, titanium, zirconium, hafnium, vanadium, chromium, molybdenum, tungsten, manganese, iron, ruthenium, osmium, cobalt, rhodium, or nickel and in particular to a process for the production of ferrocene from a mixture of FeCl2, cyclopentadiene, diethylamine, and dibenzo-18-crown-6-potassium complex followed by petroleum ether extraction.
Ferrocene (bis-cyclopentadieneyl iron, with the chemical formula Fe(C5H5)2) is an organometallic compound having the structure:
Ferrocene has numerous uses, including use as a gasoline antiknock additive (in place of tetraethyl lead), in ammonia synthesis reactions, and in fertilizer production. As a fuel catalyst for rocket propellants, ferrocene may improve combustion speed and lower the temperature of exhaust pipes. When added to fuel oils, ferrocene can help reduce smoke and air pollution, increase power and increase fuel economy. Ferrocene also has application in such diverse areas as integrated circuit manufacture, plastics stabilization, photography and printing, and biochemistry and medicine.
Prior processes for producing ferrocene have not typically been economically viable. For instance, one prior process (see U.S. Pat. No. 3,217,022) involves dissolving ferric chloride in methanol and adding iron powder. Sodium methylate and then cyclopentadiene are added, and ferrocene ultimately precipitates out of the solution. Unfortunately, this method involves large amounts of methanol, difficult purification steps to remove by-products of the process, and only results in reported yields of 65–70%.
Another method, described at http://www.orgsyn.org/orgsyn/orgsyn/prepContent.asp?prep=cv4p0473, mixes cyclopentadiene with iron chloride, diethylamine, and tetrahydroamine. This method takes several hours of vigorous stirring. This method also involves large amounts of solvent and significant and difficult preparatory treatments, such as peroxide removal and drying.
Still another prior process involves a two step process using tetrahydrofuran to form ferric chloride, FeCl2, followed by reaction of the FeCl2 with sodium cyclopentadiene under a nitrogen atmosphere. Ferrocene is then extracted using petroleum ether. This process typically takes several hours, and requires use of sodium and tetrahydrofuran.
Unfortunately, these prior processes have often involved long reaction times, expensive and dangerous reagents, relatively low yields, an inability to scale to production quantities of ferrocene, and other problems. Thus, an improved method of producing ferrocene is desirable, particularly one that may also be useful in preparing other cyclopentadiene-metal compounds in addition to ferrocene.